1. Field of the Invention
Often in the oil industry it is desirable to obtain information on the physical properties of a reservoir fluid as it exists in the formation. To obtain a sample of this fluid, it is necessary to send a device which can trap a sample of the fluid, down a well penetrating the formation. The device must be able to operate in caustic environments under extreme pressure and temperature. The acquired sample is then transferred from the sampling device, under the pressure at which it was obtained, to another vessel and shipped to a laboratory for analysis. During the sampling and transfer process, it is always necessary to maintain the integrity of the vessel, avoiding any leakage from the sampling device and shipping vessel. If leakage does occur, the phase or composition of the fluid may change as the more volatile and lighter substances evolve and escape. If this occurs, the sample is no longer representative of the fluid in the formation.
Fluid samplers traditionally used, in the industry have been described in U.S. Pat. No. 4,799,389 assigned to the assignee of this invention. In general, a typical fluid sampler consists of a steel tubular housing containing an internal spring mechanism for pushing stoppers or valves outward to seal each end of the housing. The housing and one valve are usually attached to an activation head for triggering the closing of the valves. The activation head usually contains an electric motor coupled to the surface through an electrical conductor. A pulse is passed down the conductor at an appropriate time to energize the motor and trigger the closing of the valves in the sampler. This system is unreliable and often triggers prematurely before reaching the zone of interest. Moreover, it is difficult to effectively transfer the fluid sample from the sampling device to another vessel without experiencing some leakage. In addition, the sampling device often leaks because of the internal pressures exerted upon the valves as the sampler is raised to the surface.
It is an object of this invention to provide an apparatus for reliably collecting fluid samples from desired depths.
It is also an object of this invention to provide an apparatus which will not leak once the fluid has been sampled, thereby not allowing important constituents of the fluid to escape.